Urinary incontinence is an involuntary discharge of urine from the bladder. Incontinence can be caused by a variety of factors including pregnancy, estrogen deficiency, general weakening of the sphincter or pelvic floor muscles, surgery along the urinary tract, infection, and other maladies localized in the urinary tract. This condition is widespread and affects millions of people.
There are several types of incontinence including stress incontinence, urge incontinence, and total incontinence. Stress incontinence occurs when a person's body is under physical stress. People suffering from this type of incontinence might experience urine discharge during physically stressful events. Examples of stressful events include coughing, laughing, and rigorous exercise. Urge incontinence is characterized as an urgent desire to urinate and results in total discharge of the bladder. This type of incontinence can occur at any time, but frequently occurs when a person has a sudden change in their physical position. Total incontinence is characterized by a total lack of control over urine discharge and is frequently caused by a complete failure of the sphincter muscles.
Current treatments for incontinence vary widely. Many people have to wear protective underwear such as diapers or a urinary catheter that collects discharged urine. These types of control can be uncomfortable, unsightly, and socially awkward. Pelvic exercises are also used to strengthen weak pelvic muscles. However, such exercises have limited affect, especially if the person does not perform the exercises properly or on a regular basis. Additionally, surgery is often performed to tighten the sphincter muscles. Surgery is a rather severe treatment and is typically performed as a last resort if all other treatments fail.
Drug therapy is another alternative treatment for incontinence. The type of drug that is used can vary depending on the type and cause of incontinence. For example, menopausal and post-menopausal women often experience estrogen deficiency, which causes a variety of symptoms including a thinning of the urethral and vaginal mucosa. Thinning of the urethral mucosa can result in a lack of urethral pressure and thus stress incontinence. Estrogen replacement therapy may help to control menopause related incontinence because some of the estrogen will reach and stimulate the estrogen receptors in the urethral wall. The stimulation will trigger an increase in the thickness of the urethral mucosa, which increases urethral pressure and helps to control incontinence.
In practice, estrogen is administered vaginally, orally, or transdermally. These forms of administration can cause serious side effects because the estrogen is exposed to normal and healthy tissue outside the urinary tract, which is the desired treatment area. Examples of possible side effects include breast tenderness, vaginal bleeding, cancer such as endometrial carcinoma, susceptibility to hypertension, and risk of abnormal blood clotting. The risk of side effects is even greater if there is sustained use of estrogen over a prolonged period. Therefore, estrogen replacement therapy may carry too much risk if the only or main goal of the therapy is to treat incontinence.
Another problem with estrogen replacement therapy is that tissue other than the urethral wall will absorb a significant portion of the dose. Thus, a larger dose must be administered in order to get an effective amount of estrogen to the urinary tract. The difficulty is that use of a larger dose of estrogen increases the risk of side effects and also causes an increase in the amount of waste because tissue outside the target area will absorb a larger amount of estrogen.
Other agents that increase the tone of the internal and external sphincter muscles may be used to treat incontinence. Examples of these agents include sympathomimetics such as .alpha.-adrenergic agonists and nicotinic cholinergic agonists. However, current methods of delivering these agents have problems similar to the method for delivering estrogens. That is, areas outside the urinary tract are exposed to the agent, which increases the risk of side effects. For example, sympathomimetics can result in elevated blood pressure, stimulation of the central nervous system resulting in insomnia and anxiety, dizziness, tremors, and cardiac arrhythmias. Nicotinic cholinergic agonists can also have harmful effects because there are nicotinic cholinergic receptors in the skeletal muscles, autonomic ganglia, and the adrenal medulla. Thus, treatment using nicotinic cholinergic agonists also can cause a variety of side effects.
Incontinence and current methods for treating incontinence can have a very harmful effect on a person's social, psychological, and physical well being. The involuntary discharge of urine in a public place is embarrassing if the person is not wearing any type of protective underwear or a collection catheter. It can also cause great discomfort. As a result, many people might limit their social interaction outside the privacy of their home. Even if people do wear protective underwear or a catheter, they often cause unsightly and telling bulges in the clothing. Other forms of control also have limitations. For example, many people do not perform pelvic exercises properly or on a regular basis, which limits the exercise's effectiveness. Additionally, surgery can be dangerous and is only performed as a last result.
Regarding the use of agents for treating incontinence, current delivery techniques expose the agent to tissue outside of the desired treatment area, which is an inefficient use of the agent and dramatically increases the risk of side effects. Therefore, there is a need in the art for a method of delivering an agent that can treat incontinence with a reduced risk of side effects.